Well, it's easy actually, and once you start doing things this way you'll be glad you did- it allows for much more freedom with the animations, not to mention a nearly unlimited amount of space. What you do is this:
Go to the animations 2 tab.
Now I haven't used 2K3 in a while, but in the animations 2 section there should be a menu that looks like this, probably under the third tab for a given character in that section:
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The TEXT represents the names for each of the animations in the animations two tab for whichever character you are examining.
The thing in the middle is a scroll bar.
The stuff on the right is a black preview window.
Somewhere around the bottom right of that part of the menu, you should see two circles, like the ones you click to select an option. Click the one that says use battle animation.
Select an animation to use for that motion.
This way, you can have elaborate poses for your characters, as well as extremely detailed and fluid animations for attacking, defending, or just about anything!